430 lines
14 KiB
C
430 lines
14 KiB
C
/* Very basic LWIP & FreeRTOS-based DHCP server
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*
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* Based on RFC2131 http://www.ietf.org/rfc/rfc2131.txt
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* ... although not fully RFC compliant yet.
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*
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* TODO
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* * Allow binding on a single interface only (for mixed AP/client mode), lwip seems to make it hard to
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* listen for or send broadcasts on a specific interface only.
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*
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* * Probably allocates more memory than it should, it should be possible to reuse netbufs in most cases.
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*
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* Part of esp-open-rtos
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* Copyright (C) 2015 Superhouse Automation Pty Ltd
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* BSD Licensed as described in the file LICENSE
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*/
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#include <string.h>
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#include <strings.h>
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#include <FreeRTOS.h>
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#include <task.h>
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#include <lwip/netif.h>
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#include <lwip/api.h>
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#include "esplibs/libmain.h"
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#if (DHCP_DEBUG == LWIP_DBG_ON)
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#define debug(s, ...) printf("%s: " s "\n", "DHCP", ## __VA_ARGS__)
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#else
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#define debug(s, ...)
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#endif
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/* Grow the size of the lwip dhcp_msg struct's options field, as LWIP
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defaults to a 68 octet options field for its DHCP client, and most
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full-sized clients send us more than this. */
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#define DHCP_OPTIONS_LEN 312
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#include <lwip/ip.h>
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#include <lwip/prot/dhcp.h>
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#include <lwip/prot/iana.h>
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_Static_assert(sizeof(struct dhcp_msg) == offsetof(struct dhcp_msg, options) + 312, "dhcp_msg_t should have extended options size");
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#include <lwip/netbuf.h>
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#include "dhcpserver.h"
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typedef struct {
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uint8_t hwaddr[NETIF_MAX_HWADDR_LEN];
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uint8_t active;
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uint32_t expires;
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} dhcp_lease_t;
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typedef struct {
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struct netconn *nc;
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uint8_t max_leases;
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ip4_addr_t first_client_addr;
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struct netif *server_if;
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dhcp_lease_t *leases; /* length max_leases */
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/* Optional router */
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ip4_addr_t router;
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/* Optional DNS server */
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ip4_addr_t dns;
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} server_state_t;
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/* Only one DHCP server task can run at once, so we have global state
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for it.
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*/
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static TaskHandle_t dhcpserver_task_handle = NULL;
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static server_state_t *state;
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/* Handlers for various kinds of incoming DHCP messages */
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static void handle_dhcp_discover(struct dhcp_msg *received);
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static void handle_dhcp_request(struct dhcp_msg *dhcpmsg);
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static void handle_dhcp_release(struct dhcp_msg *dhcpmsg);
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static void send_dhcp_nak(struct dhcp_msg *dhcpmsg);
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static void dhcpserver_task(void *pxParameter);
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/* Utility functions */
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static uint8_t *find_dhcp_option(struct dhcp_msg *msg, uint8_t option_num, uint8_t min_length, uint8_t *length);
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static uint8_t *add_dhcp_option_byte(uint8_t *opt, uint8_t type, uint8_t value);
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static uint8_t *add_dhcp_option_bytes(uint8_t *opt, uint8_t type, void *value, uint8_t len);
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static dhcp_lease_t *find_lease_slot(uint8_t *hwaddr);
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/* Copy IP address as dotted decimal to 'dest', must be at least 16 bytes long */
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inline static void sprintf_ipaddr(const ip4_addr_t *addr, char *dest)
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{
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if (addr == NULL)
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sprintf(dest, "NULL");
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else
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sprintf(dest, "%d.%d.%d.%d", ip4_addr1(addr),
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ip4_addr2(addr), ip4_addr3(addr), ip4_addr4(addr));
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}
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void dhcpserver_start(const ip4_addr_t *first_client_addr, uint8_t max_leases)
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{
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/* Stop any existing running dhcpserver */
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if (dhcpserver_task_handle)
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dhcpserver_stop();
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state = malloc(sizeof(server_state_t));
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memset(state, 0, sizeof(*state));
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state->max_leases = max_leases;
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state->leases = calloc(max_leases, sizeof(dhcp_lease_t));
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bzero(state->leases, max_leases * sizeof(dhcp_lease_t));
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// state->server_if is assigned once the task is running - see comment in dhcpserver_task()
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ip4_addr_copy(state->first_client_addr, *first_client_addr);
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/* Clear options */
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ip4_addr_set_zero(&state->router);
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ip4_addr_set_zero(&state->dns);
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xTaskCreate(dhcpserver_task, "DHCP Server", 448, NULL, 2, &dhcpserver_task_handle);
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}
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void dhcpserver_stop(void)
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{
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if (dhcpserver_task_handle) {
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vTaskDelete(dhcpserver_task_handle);
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dhcpserver_task_handle = NULL;
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if (state->nc)
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netconn_delete(state->nc);
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free(state->leases);
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free(state);
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state = NULL;
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}
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}
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void dhcpserver_set_router(const ip4_addr_t *router)
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{
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ip4_addr_copy(state->router, *router);
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}
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void dhcpserver_set_dns(const ip4_addr_t *dns)
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{
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ip4_addr_copy(state->dns, *dns);
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}
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static void dhcpserver_task(void *pxParameter)
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{
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/* netif_list isn't assigned until after user_init completes, which is why we do it inside the task */
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state->server_if = netif_list; /* TODO: Make this configurable */
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state->nc = netconn_new (NETCONN_UDP);
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if(!state->nc) {
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debug("DHCP Server Error: Failed to allocate socket.");
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return;
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}
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netconn_bind(state->nc, IP4_ADDR_ANY, LWIP_IANA_PORT_DHCP_SERVER);
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netconn_bind_if (state->nc, netif_get_index(state->server_if));
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while(1)
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{
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struct netbuf *netbuf;
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struct dhcp_msg received = { 0 };
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/* Receive a DHCP packet */
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err_t err = netconn_recv(state->nc, &netbuf);
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if(err != ERR_OK) {
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debug("DHCP Server Error: Failed to receive DHCP packet. err=%d", err);
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continue;
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}
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/* expire any leases that have passed */
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uint32_t now = xTaskGetTickCount();
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for (int i = 0; i < state->max_leases; i++) {
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if (state->leases[i].active) {
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uint32_t expires = state->leases[i].expires - now;
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if (expires >= 0x80000000) {
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state->leases[i].active = 0;
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}
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}
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}
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ip_addr_t received_ip;
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u16_t port;
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netconn_addr(state->nc, &received_ip, &port);
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if (netbuf_len(netbuf) < offsetof(struct dhcp_msg, options)) {
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/* too short to be a valid DHCP client message */
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netbuf_delete(netbuf);
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continue;
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}
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if(netbuf_len(netbuf) >= sizeof(struct dhcp_msg)) {
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debug("DHCP Server Warning: Client sent more options than we know how to parse. len=%d", netbuf_len(netbuf));
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}
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netbuf_copy(netbuf, &received, sizeof(struct dhcp_msg));
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netbuf_delete(netbuf);
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uint8_t *message_type = find_dhcp_option(&received, DHCP_OPTION_MESSAGE_TYPE,
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DHCP_OPTION_MESSAGE_TYPE_LEN, NULL);
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if(!message_type) {
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debug("DHCP Server Error: No message type field found");
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continue;
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}
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#if (DHCP_DEBUG == LWIP_DBG_ON)
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debug("State dump. Message type %d", *message_type);
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for(int i = 0; i < state->max_leases; i++) {
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dhcp_lease_t *lease = &state->leases[i];
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debug("lease slot %d expiry %d hwaddr %02x:%02x:%02x:%02x:%02x:%02x", i, lease->expires, lease->hwaddr[0],
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lease->hwaddr[1], lease->hwaddr[2], lease->hwaddr[3], lease->hwaddr[4],
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lease->hwaddr[5]);
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}
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#endif
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switch(*message_type) {
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case DHCP_DISCOVER:
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handle_dhcp_discover(&received);
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break;
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case DHCP_REQUEST:
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handle_dhcp_request(&received);
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break;
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case DHCP_RELEASE:
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handle_dhcp_release(&received);
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break;
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default:
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debug("DHCP Server Error: Unsupported message type %d", *message_type);
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break;
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}
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}
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}
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static void handle_dhcp_discover(struct dhcp_msg *dhcpmsg)
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{
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if (dhcpmsg->htype != LWIP_IANA_HWTYPE_ETHERNET)
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return;
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if (dhcpmsg->hlen > NETIF_MAX_HWADDR_LEN)
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return;
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dhcp_lease_t *freelease = find_lease_slot(dhcpmsg->chaddr);
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if(!freelease) {
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debug("DHCP Server: All leases taken.");
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return; /* Nothing available, so do nothing */
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}
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/* Reuse the DISCOVER buffer for the OFFER response */
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dhcpmsg->op = DHCP_BOOTREPLY;
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bzero(dhcpmsg->options, DHCP_OPTIONS_LEN);
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dhcpmsg->yiaddr.addr = lwip_htonl(lwip_ntohl(state->first_client_addr.addr) + (freelease - state->leases));
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uint8_t *opt = (uint8_t *)&dhcpmsg->options;
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opt = add_dhcp_option_byte(opt, DHCP_OPTION_MESSAGE_TYPE, DHCP_OFFER);
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opt = add_dhcp_option_bytes(opt, DHCP_OPTION_SERVER_ID, &state->server_if->ip_addr, 4);
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opt = add_dhcp_option_bytes(opt, DHCP_OPTION_SUBNET_MASK, &state->server_if->netmask, 4);
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if (!ip4_addr_isany_val(state->router)) {
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opt = add_dhcp_option_bytes(opt, DHCP_OPTION_ROUTER, &state->router, 4);
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}
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if (!ip4_addr_isany_val(state->dns)) {
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opt = add_dhcp_option_bytes(opt, DHCP_OPTION_DNS_SERVER, &state->dns, 4);
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}
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opt = add_dhcp_option_bytes(opt, DHCP_OPTION_END, NULL, 0);
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struct netbuf *netbuf = netbuf_new();
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netbuf_alloc(netbuf, sizeof(struct dhcp_msg));
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netbuf_take(netbuf, dhcpmsg, sizeof(struct dhcp_msg));
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netconn_sendto(state->nc, netbuf, IP_ADDR_BROADCAST, 68);
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netbuf_delete(netbuf);
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}
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static void handle_dhcp_request(struct dhcp_msg *dhcpmsg)
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{
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static char ipbuf[16];
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if (dhcpmsg->htype != LWIP_IANA_HWTYPE_ETHERNET)
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return;
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if (dhcpmsg->hlen > NETIF_MAX_HWADDR_LEN)
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return;
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ip4_addr_t requested_ip;
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uint8_t *requested_ip_opt = find_dhcp_option(dhcpmsg, DHCP_OPTION_REQUESTED_IP, 4, NULL);
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if (requested_ip_opt) {
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memcpy(&requested_ip.addr, requested_ip_opt, 4);
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} else if (ip4_addr_cmp(&requested_ip, IP4_ADDR_ANY4)) {
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ip4_addr_copy(requested_ip, dhcpmsg->ciaddr);
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} else {
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debug("DHCP Server Error: No requested IP");
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send_dhcp_nak(dhcpmsg);
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return;
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}
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/* Test the first 4 octets match */
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if (ip4_addr1(&requested_ip) != ip4_addr1(&state->first_client_addr)
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|| ip4_addr2(&requested_ip) != ip4_addr2(&state->first_client_addr)
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|| ip4_addr3(&requested_ip) != ip4_addr3(&state->first_client_addr)) {
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sprintf_ipaddr(&requested_ip, ipbuf);
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debug("DHCP Server Error: %s not an allowed IP", ipbuf);
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send_dhcp_nak(dhcpmsg);
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return;
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}
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/* Test the last octet is in the MAXCLIENTS range */
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int16_t octet_offs = ip4_addr4(&requested_ip) - ip4_addr4(&state->first_client_addr);
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if(octet_offs < 0 || octet_offs >= state->max_leases) {
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debug("DHCP Server Error: Address out of range");
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send_dhcp_nak(dhcpmsg);
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return;
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}
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dhcp_lease_t *requested_lease = state->leases + octet_offs;
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if (requested_lease->active && memcmp(requested_lease->hwaddr, dhcpmsg->chaddr,dhcpmsg->hlen))
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{
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debug("DHCP Server Error: Lease for address already taken");
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send_dhcp_nak(dhcpmsg);
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return;
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}
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memcpy(requested_lease->hwaddr, dhcpmsg->chaddr, dhcpmsg->hlen);
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sprintf_ipaddr(&requested_ip, ipbuf);
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debug("DHCP lease addr %s assigned to MAC %02x:%02x:%02x:%02x:%02x:%02x", ipbuf, requested_lease->hwaddr[0],
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requested_lease->hwaddr[1], requested_lease->hwaddr[2], requested_lease->hwaddr[3], requested_lease->hwaddr[4],
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requested_lease->hwaddr[5]);
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uint32_t now = xTaskGetTickCount();
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requested_lease->expires = now + DHCPSERVER_LEASE_TIME * configTICK_RATE_HZ;
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requested_lease->active = 1;
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sdk_wifi_softap_set_station_info(requested_lease->hwaddr, &requested_ip);
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/* Reuse the REQUEST message as the ACK message */
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dhcpmsg->op = DHCP_BOOTREPLY;
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bzero(dhcpmsg->options, DHCP_OPTIONS_LEN);
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ip4_addr_copy(dhcpmsg->yiaddr, requested_ip);
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uint8_t *opt = (uint8_t *)&dhcpmsg->options;
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opt = add_dhcp_option_byte(opt, DHCP_OPTION_MESSAGE_TYPE, DHCP_ACK);
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uint32_t expiry = htonl(DHCPSERVER_LEASE_TIME);
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opt = add_dhcp_option_bytes(opt, DHCP_OPTION_LEASE_TIME, &expiry, 4);
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opt = add_dhcp_option_bytes(opt, DHCP_OPTION_SERVER_ID, &state->server_if->ip_addr, 4);
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opt = add_dhcp_option_bytes(opt, DHCP_OPTION_SUBNET_MASK, &state->server_if->netmask, 4);
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if (!ip4_addr_isany_val(state->router)) {
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opt = add_dhcp_option_bytes(opt, DHCP_OPTION_ROUTER, &state->router, 4);
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}
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if (!ip4_addr_isany_val(state->dns)) {
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opt = add_dhcp_option_bytes(opt, DHCP_OPTION_DNS_SERVER, &state->dns, 4);
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}
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opt = add_dhcp_option_bytes(opt, DHCP_OPTION_END, NULL, 0);
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struct netbuf *netbuf = netbuf_new();
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netbuf_alloc(netbuf, sizeof(struct dhcp_msg));
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netbuf_take(netbuf, dhcpmsg, sizeof(struct dhcp_msg));
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netconn_sendto(state->nc, netbuf, IP_ADDR_BROADCAST, 68);
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netbuf_delete(netbuf);
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}
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static void handle_dhcp_release(struct dhcp_msg *dhcpmsg)
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{
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dhcp_lease_t *lease = find_lease_slot(dhcpmsg->chaddr);
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if (lease) {
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lease->active = 0;
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lease->expires = 0;
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}
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}
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static void send_dhcp_nak(struct dhcp_msg *dhcpmsg)
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{
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/* Reuse 'dhcpmsg' for the NAK */
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dhcpmsg->op = DHCP_BOOTREPLY;
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bzero(dhcpmsg->options, DHCP_OPTIONS_LEN);
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uint8_t *opt = (uint8_t *)&dhcpmsg->options;
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opt = add_dhcp_option_byte(opt, DHCP_OPTION_MESSAGE_TYPE, DHCP_NAK);
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opt = add_dhcp_option_bytes(opt, DHCP_OPTION_SERVER_ID, &state->server_if->ip_addr, 4);
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opt = add_dhcp_option_bytes(opt, DHCP_OPTION_END, NULL, 0);
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struct netbuf *netbuf = netbuf_new();
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netbuf_alloc(netbuf, sizeof(struct dhcp_msg));
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netbuf_take(netbuf, dhcpmsg, sizeof(struct dhcp_msg));
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netconn_sendto(state->nc, netbuf, IP_ADDR_BROADCAST, 68);
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netbuf_delete(netbuf);
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}
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static uint8_t *find_dhcp_option(struct dhcp_msg *msg, uint8_t option_num, uint8_t min_length, uint8_t *length)
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{
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uint8_t *start = (uint8_t *)&msg->options;
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uint8_t *msg_end = (uint8_t *)msg + sizeof(struct dhcp_msg);
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for (uint8_t *p = start; p < msg_end-2;) {
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uint8_t type = *p++;
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uint8_t len = *p++;
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if (type == DHCP_OPTION_END)
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return NULL;
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if (p+len >= msg_end)
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break; /* We've overrun our valid DHCP message size, or this isn't a valid option */
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if (type == option_num) {
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if (len < min_length)
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break;
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if (length)
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*length = len;
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return p; /* start of actual option data */
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}
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p += len;
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}
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return NULL; /* Not found */
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}
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static uint8_t *add_dhcp_option_byte(uint8_t *opt, uint8_t type, uint8_t value)
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{
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*opt++ = type;
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*opt++ = 1;
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*opt++ = value;
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return opt;
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}
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static uint8_t *add_dhcp_option_bytes(uint8_t *opt, uint8_t type, void *value, uint8_t len)
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{
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*opt++ = type;
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if (len) {
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*opt++ = len;
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memcpy(opt, value, len);
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}
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return opt+len;
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}
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/* Find a free DHCP lease, or a lease already assigned to 'hwaddr' */
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static dhcp_lease_t *find_lease_slot(uint8_t *hwaddr)
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{
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dhcp_lease_t *empty_lease = NULL;
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for (int i = 0; i < state->max_leases; i++) {
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if (!state->leases[i].active && !empty_lease)
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empty_lease = &state->leases[i];
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else if (memcmp(hwaddr, state->leases[i].hwaddr, 6) == 0)
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return &state->leases[i];
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}
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return empty_lease;
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}
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